T-cell prolymphocytic leukemia (T-PLL) is typically associated with an aggressive clinical course, with a median survival of less than 1 year. We report a case of T-PLL that displays multiple cytogenetic abnormalities, with the most complex subclone having the following karyotype: 47, Y, -X, +8, inv (10) (p12q26), del (11) (p13p15) +marker. However, despite this genetic complexity, the leukemia has behaved in a remarkably indolent manner, with the patient remaining asymptomatic, without therapeutic intervention, for more than 7 years. The unusually benign behavior of this disease calls into question the validity of grouping such cases under the umbrella of T-PLL and warrants a reconsideration of T-cell chronic lymphocytic leukemia (no longer recognized as a distinct disease) as a bona fide diagnostic entity.